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U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE.
Washington, D.C. 20590
May 26, 2011
In Reply Refer To: HOTO-1
Mr. Arlen Yost
OMJC Signal, Inc.
P.O. Box 1594
Waterloo, IA 50704
Dear Mr. Yost:
Thank you for your e-mail May 9 to Mr. Scott Wainwright of our Manual on Uniform Traffic Control Devices (MUTCD) Team requesting an Official Interpretation of the MUTCD regarding whether conflict monitoring of temporary and portable traffic signals is required, recommended, or optional. You asked for an update of unofficial guidance that Mr. Wainwright had provided in a February, 2006, email to another supplier of temporary and portable traffic signals, and you asked several specific questions on this subject.
It is our Official Interpretation that the use of a conflict monitor with all temporary and portable traffic signals used in a temporary traffic control zone unless such signals are manually controlled by an on-site flagger or other means that the highway agency determines to be adequate to prevent the display of conflicting indications. The use of a conflict monitor with temporary and portable traffic signals is a Guidance ("should") condition in the MUTCD and highway agencies should only deviate from this recommended practice based on an engineering study or engineering judgment. Our reasoning for this interpretation is as follows:
The language in the MUTCD pertinent to the issue at hand has been revised since the unofficial guidance was provided in 2006. That guidance cited the 2003 edition of the MUTCD, which has been superseded by the 2009 edition. The pertinent text of the 2009 MUTCD is as follows:
Paragraph 05 of Section 6F.84 and paragraph 01 of Section 4H.02, taken in context with the other provisions cited above, mean that a conflict monitor should be used with all temporary and portable traffic signals. The language gives highway agencies the flexibility to determine, based on an engineering study or engineering judgment regarding the particular conditions of a site or temporary traffic control zone, that the Section 4H.02 requirement for an "adequate means to prevent conflicting situations" can be satisfied by something other than a conflict monitor.
Some highway agencies have determined that, under some conditions, electronic means other than physical interconnection and conflict monitor(s) provides an adequate means to prevent conflicting displays as Section 4H.02 requires. Some highway agencies have also determined that, in the case of temporary or portable traffic signals that are manually operated by an on-site flagger, the ability of the flagger to intervene if a malfunction occurs is adequate to prevent conflicting indications. In any event, it is incumbent on the highway agency, not the manufacturer or supplier, to make determinations such as these and to be able to defend their engineering reasons in the event a tort liability case arises at a particular site.
Thank you for writing on this subject. Please note that we have assigned your request the following official interpretation number and title: "4(09)-10 (I) – Conflict Monitoring of Temporary and Portable Signals." Please refer to this number in any future correspondence regarding this issue.
Original signed by:
Mark R. Kehrli
Director, Office of Transportation Operations
United States Department of Transportation - Federal Highway Administration